Coaxial cable connection system

ABSTRACT

For connecting a coaxial cable to a tap box housing a highfrequency circuit, a first connector element comprising an outer conductor is secured to the box and is provided with a center contact which is secured at one end to the circuit, the other end being a socket with a conical bore. A second connector element is secured to the face end of the first element and includes an outer cylindrical member secured to the outer conductor of the cable and having centrally located spring fingers through which the inner conductor of the cable extends, the spring fingers being forced to grip the center conductor where the spring fingers enter the conical bore when the two connector elements are assembled.

United States Patent [72] Inventor Edgar Wilmot Forney, Jr.

Harrisburg, Pa.

[21] Appl. No. 15,178

[22] Filed Feb. 27, I970 Patented Nov. 23, 1971 73 Assignee AMPIncorporated Harrisburg, Pa.

[54] COAXIAL CABLE CONNECTION SYSTEM 4 Claims, 4 Drawing Figs.

1 52] US. Cl 339/89 C, 339/177 E [51] Int. Cl ..H0lr 13/54. HOlr 17/04Field oisearch 339/ C,

89C, 90C,9l P, 94C, 126.1, 103 B, 177 R, 177 E, R, 268, 273, 276 T;174/75 C, 88 C, 89

[56] References Cited UNITED STATES PATENTS 2,454,829 11/1948 Neijstrom339/268 S 2,860,316 11/1958 Watterset alt. 339/89 C 3,147,057 9/1964ColusSi 339/89 C 3,292,136 12/1966 Somerset, 339/177 E 34 l 6 20/ S 2 y3,291,895 12/1966 Van Dyke 174/88 C 3,526,871 9/1970 Hobart; 339/177 EFOREIGN PATENTS 828,886 12/1969 Canada 339/177 E 1,470,206 l/l967 France339/177 R ABSTRACT: For connecting a coaxial cable to a tap box housinga high-frequency circuit, a first connector element comprising an outerconductor is secured to the box and is provided with a center contactwhich is secured at one end to the circuit, the other end being a socketwith a conical bore. A second connector element is secured to the faceend of the first element and includes an outer cylindrical membersecured to the outer conductor of the cable and having centrally locatedspring fingers through which the inner conductor of the cable extends.the spring fingers being forced to grip the center conductor where thespring fingers enter the conical bore when the two connector elementsare assembled.

PATENTEUNuv 23 I97! 3, 622. 939

SHEET 2 OF 2 COAXIAL CABLE CONNECTION SYSTEM The invention relates toimprovements in coaxial cable connection system.

High-frequency signal-distribution systems which transmit audio andvideo signals over coaxial transmission lines are in wide use today. Oneexample is known as community antenna television (CATV). Enclosurecontaining amplification circuitry are 'located at various points in thecable system to maintain the signal level. To distribute the signals tovarious subscribers, tap boxes are spaced along the cable from whichindividual lines lead to each subscriber. Since the boxes, in manyinstances, are exposed to weather conditions, the coaxial connectordevices to be tapped into the boxes must' be weatherproof. They must beso constructed that no positive axial forces be transmitted through thecenter contact of the connector part extending into the box andconnected to the circuit or component therein which may be part of arelatively fragile printed circuit board. On the other hand they mustresist axial forces in the opposite direction which will causedisconnects from the circuitry. Such axial forces are caused bydifferential thermal expansion and contraction of the coaxial cablecenter conductor and shield or physical forces due to wind, snow load,etc.

The coaxial connection system disclosed herein has been developed toovercome the many problems and to simplify the application of coaxialconnectors in cabled radio frequency systems. Their use is not limitedto this application, but may be adapted anywhere that some or all of theadvantages of this structure are applicable. Basically, the coaxialconnection is made between the coaxial cable and an adapter which adaptsany coaxial cable to mate into either a universal receptacle whichinterfaces with system components, or into either side of a universalsplice. The above-mentioned universal receptacle with which theconnector mates, allows the supplier of system components, such asamplifiers, splitters, etc., to standardize on one connector receptacle,simplifying both electrical and mechanical matching problems.

The universal receptacle as hereinbelow described is essentially acoaxial plug member provided by a hollow conductive shell which isthreaded at its forward end for insertion into a threaded socket in atap box housing a circuit such as, for example, a directional couplerwhich is utilized in CATV systems to direct signals on the transmissionline to a subscriber. The center contact of the receptacle, which issecured in insulated relation thereto, is provided by a rearwardlyfacing socket for receiving the center contact of a coaxial line and acontact member extending forwardly of the shell member for connectionwith the input or output of the circuit or component within the box. Thecoupling member which adapts the coaxial cable for electrical andmechanical connection to the housing is secured at its rearward endportion to the cable outer conductor and is provided with a concentriccollet comprising spring fingers through which the inner conductor ofthe cable extends. As the coupling member is being secured at itsforward end to the rear end of the receptacle, as by a threadedconnection, the collet and center conductor of the cable therewithin aremoved into the socket of the receptacle, which has a conical recess, andoperates to force the spring fingers of the collet against the centerconductor.

It is therefore an object of the invention to provide a coaxial lineconnector which is waterproof.

A further object of the invention is to provide a connector for acoaxial line which resists pull out of the conductors in use.

Another object of this invention is to provide a connector for coaxiallines which is especially adapted for connection to a circuit componentshoused in a tap box and which will transmit a minumum of axial forcescaused by temperature changes.

lt is a still further object of the invention to provide a coaxiallcable connector which is comprised of a universal receptacle and anattachable cable adapter in which the receptacle may be utilized withcables of different sizes.

With the above objects in view, together with other and further objectsthereof, the following description with particular reference to thedrawings should provide a full understanding of the invention.

FIG. 1 is a perspective view of the tap box on which the receptacle, aspart of the connector assembly, is mounted;

FIG. 2 is a view in cross section of the receptacle and cable adapterassembly with the cable secured therein;

FIG. 3 is a perspective view of the spring clamp within the cableadapter; and

FIG. 4 is a longitudinal cross-sectional view of the receptacle andcable adapter in assembled relation.

With reference to FIG. 1, there is shown a tap box B, which usuallyhouses a component circuit of a CATV system such as a directionalcoupler or an amplifier. The tap box B may be suspended from a messengercable for connection to the coaxial cable L, although it may beunderground or on a wall of a buildingQ'ln any case, the tap box isprovided with at least a pair of threaded openings, only one of which,such as 2, is shown, through which the input and output conductorsrespectively extend. The universal receptacle 4 is provided at itsforward end with threads 6 for interengaging with the threads in opening2 of the box. The receptacle 4 comprises a hollow cylindrical memberopen at both ends and provided with four concentric bores 8, l0, l2 and14 which respectively decrease in diameter from the rear end into whichthe cable can'ying coupling member enters. Each of the three largerbores provides an annular wall 16, 18 and 20 at their respectivejunctions with the smaller bores. Extending across the bore 12 andagainst the wall 20 is a centrally apertured dielectric bead 22 havinghigh resistance to bending. The thickness of the bead is substantiallythe axial extent of the bore 12 so that the edge portion of the wall 18may be spun over against the forward edge of the bead to secure itwithin the receptacle and against the shoulder 20.

A center contact supported by the bead 22 is provided by a cylindricalsocket member 24 extending axially from the rear face of the beadcentrally of the bore 10 and an integrally formed stem portion 26 ofsmaller diameter than the socket portion extending forwardly through theaperture in the bead. A wall 28 of the center contact, provided at thejunction of stem portion 26 and socket member 24 abuts the rear face ofbead 22, while a sleeve 32 of a larger outer diameter than the stemportion is crimped to the projecting portion thereof and abuts theopposite side of the bead. The center contact is thus captivated by thebead and can withstand large forces tending to move it axially eitherrearwardly or forwardly. The other end of sleeve 32 is crimped to aconductive axial extension 30 of the stem portion which projectsforwardly of the shell member 4 for connection with a terminal withinthe tap box when the receptacle is mounted thereon. The socket member isprovided at its rear end with a central tapered recess which divergesoutwardly.

The inner wall of the large bore 8 of the shell member 4 is threaded asat 34 to threadably receive therein a cable adapter comprising couplingnut assembly 35 which is externally threaded to cooperate with thethread 34. The coupling nut assembly comprises a hollow cylindricalshell member 36 hav ing a bore 38 of a predetermined diameter opening atits forward end. Slidably and rotatably mounted within the bore 38 is aninner ferrule assembly comprising a ferrule 40 having a rearwardly openbore 42 of a predetermined diameter to closely encompass the semirigidouter conductor of a coaxial cable such as line L. Intermediate the endsof the ferrule 40 the diameter of the bore is abruptly reduced leaving arearwardly facing wall 44 against which the end of the outer conductorof the line L abuts. The extreme forward end of the ferrule is providedwith an opening 46 of somewhat larger diameter than bore 42 and whichextends inwardly for a predetermined distance to present a forwardlyfacing circumferential wall 48. A centrally apertured dielectric bead 50extends across the opening 46 and against the wall 48. The bead 50 has athickness substantially equal to the depth of the opening 46 IOIOIISJand is held therein by the material of the forward edge of the ferrulewhich is spun over and about the forward edge portion of the bead. Theforward end portion of the ferrule is provided with a reduced outerdiameter, to leave a forwardly facing circumferential shoulder 45 whichabuts the intumed edge portion of the forward end of the shell member 36to prevent outward movement of the ferrule.

Rearwardly of the bore 38 in the coupling nut assembly, the shell member36 is provided with a central opening 52 of a diameter substantially thesame as bore 42 and the outer diameter of the outer conductor of theline L.

Intermediate the opening 52 and bore 38 in shell member 36 is an opening54 of a diameter which is slightly larger than the the diameter ofopening 52. A tapered inner wall 56 leads from smaller opening 52 intolarger opening 54. Normally seated against the wall of opening 54 andextending into bore 38 is a spring clamp 58 in the form of a C which isof an axial length to extend between the tapered wall 56 and the rearend wall of the ferrule 40 within bore 38. The radial thickness of theclamp 58 is substantially the difference between the radii of openings52 and 54, so that it does not obstruct entry of line L when normallyseated against the wall of opening 54. The inner surface of the clamp isprovided with circumferential grooves 59, the lands between the groovesbeing rounded to form in effect blunted serrations. The near end of theshell 36 is provided with a bore 60 which is internally threaded tocooperate with an externally threaded gland nut 62. Between the enlargedbore 60 and smaller opening 52 is formed a rearwardly facing bottomwall, so that by placing a washer of sealant material 64, such asunvulcanized soft butyl rubber, against the bottom of the bore 60 andtightening of the gland nut, the sealant will be forced against thebottom wall and be distributed evenly about the cable at its entranceinto opening 52.

Supported within the central aperture of the bead 50 is a collet 66. Thecollet comprises a hollow tubular member longitudinally slotted at itsforward end to form a plurality of spring fingers 68. The oppositeunslotted end at the rear of the collet extends through the centralopening in the bead and the preformed shoulder 70 of the collet locks itin place to prevent forward axial movement thereof. Forwardly of itsrear end, the collet is provided with a thickened peripheral bead orshoulder 72 having a rearward face abutting the forward face of thebead, whereby the collet is captivated and pullout is prevented. Theinner surfaces of the spring fingers 68 are provided with serrations inplanes normal to the axis of the collet for gripping a wire 74 locatedwithin the fingers.

In use, the receptacle 4 is first threaded into an opening in the tapbox B with the conductive member 30 effecting electrical contact with aterminal of a circuit housed in the box. The cable to be clamped to thecable adapter is prepared by first removing a length of outer insulationfrom an end of the cable to bare a short length of outer conductor. Anend portion of the outer conductor and inner dielectric is then removedto expose a length of inner conductor 74. The gland nut 62 is thenslipped over the outer conductor and the cable end inserted into thecoupling nut assembly 35 including the ferrule 40 until the end of theouter conductor abuts the end of the wall 44 of the ferrule. At the sametime, the inner conductor 74 extends through the interior of collet 66including the spring fingers 68. The forward end of the coupling nutassembly 35, with the cable end disposed therein, is then threaded intothe rear opening 8 of the receptacle 4. The shell member 36 of thecoupling nut assembly is rotatable relative to the ferrule 40, asexplained heretofore, and as the shell member advances within thereceptacle 4 by continued rotation thereof, the tapered wall 56 forcesthe clamp member 58 against the rear edge of ferrule 40. Since the edgeof the opening 42 in the latter is chamfered as at 43, such chamferededge at one end of the clamp and the tapered wall 56 at the other end ofthe clamp provide camming surfaces which cause the clamp to becompressed radially inward against the outer conductor of the cabletherein as the shell moves inwardly. Simultaneously, during such forwardmovement of shell 36. the spring fingers 68 within the substantiallyconical opening in socket member 24 will be forced against the conductor74 by the wall of the opening to grip the conductor and provide a securemechanical and electrical connection, thereto. Both the receptacle 4 andshell member 36 are provided on their outer surfaces with flat portionsfor engagement by a wrench for easy assemblyor disassembly of the parts.

A shallow circumferential groove is provided in the periphery of theshell member 36 just rearwardly of its threaded portion for thereception of an O-ring 75. The rear entrance to the bore in receptacle 4is somewhat enlarged in diameter to leave a rearwardly facingcircumference shoulder 76. When the shell member 36 is fully threadedinto receptacle 4, the O-ring is compressed by the shoulder 76 toprovide a seal. A further O-ring for sealing purposes at the entrance tothe tap box is provided at the forward end of the receptacle 4.Typically, a split clamp such as shown will provide cable holdingstrength of 300-500 lbs. depending on cable size. The blunt serrationson the clamp prevent fractures due to notch effects caused by sharplands between the grooves.

The collet 66 may be provided with spring fingers 68 of differentthicknesses, so as to be capable of use with center conductors ofdifferent sizes. Positive captivity of the collet 66 by the rigiddielectric bead and high clamping force due to the action of the springfingers within the socket tends to eliminate the common center-conductorpullout failures due to the differential thermal expansion andcontraction. Preliminary tests indicate that resistance to pullout istypically in the neighborhood of 250 lbs. for No. 7AWG copper wire.Furthermore, the connectors of the system described above are reusableand the fact that the cable adapter can be disconnected from thereceptacle with which the socket member is associated, allows easyreplacement of component circuits, such as amplifiers, in the system.

Having thus described the invention as exemplified by a preferredembodiment, obvious changes and modifications by persons skilled in theart are deemed to fall within the spirit and scope of the disclosure andclaims.

1. A coaxial line terminal adapter element for detachable connection ofa receptacle, comprising:

a hollow conductor body member having a cylindrical bore therethrough,means in said bore for conductively securing the body member to the endportion of an outer conductor of a coaxial line, insulating meansmounted within the bore, a collet having an unobstructed openingtherethrough for receiving the inner conductor of the line supported bysaid insulating means centrally of the bore, the collet beinglongitudinally slotted to provide a socket having a plurality of fingersbetween which the central conductor of the coaxial line slidably extendswhen the outer conductor of the coaxial line is disposed in the bodymember, a ferrule member supporting the insulating means and slidablymounted within the cylindrical bore, means within the bore providingradially inwardly extending circumferential ledge means, the means forsecuring the body member to the outer conductor of the cable comprisinga resilient split sleeve coaxial with the bore and disposed between theledge means and an inner end wall provided on the ferrule member, saidledge means and said inner end wall being provided with camming means tocause radial compression of the sleeve in response to relative axialmovement of the ferrule and ledge means toward each other, saidreceptacle being provided with engaging means for detachably engagingthe body member, said receptacle having bearing means for bearingagainst and moving the ferrule member axially against the split sleeve,

said receptacle provided with a bore therethrough, and insulating meansprovided within the receptacle bore for supporting a conductive socketmember concentrically therewithin, said socket member including anopening to receive the spring fingers therein.

2. A coaxial line terminal adapter element for detachable connection ofa receptacle, comprising: 5

a hollow conductor body member having a cylindrical bore ing the bodymember to the end portion of an outer conductor of a coaxial line,insulating means mounted within the bore, a collet having anunobstructed opening therethrough, means in said bore for conductivelysecurtherethrough for receiving the inner conductor of the line ing thebody member to the end portion of an outer con- 5 supported by saidinsulating means centrally of the bore, ductor of a coaxial line,insulating means mounted within the collet being longitudinally slottedto provide a socket the bore, a collet having an unobstructed openinghaving a plurality of fingers between which the central therethrough forreceiving the inner conductor of the line conductor of the coaxial lineslidably extends when the supported by said insulating means centrallyof the bore, outer conductor of the coaxial line is disposed in the bodythe collet being longitudinally slotted to provide a socket member, aferrule member supporting the insulating havin a plurality of fingersbetw en which h centr l means and slidably mounted within thecylindrical bore, conductor of the coaxial line slidabl xte ds wh hmeans within the bore providing radially inwardly extendouter conductorf h i l ling i W i h b d ing circumferential ledge means, the means forsecuring member, a female member supporting the insulating the bodymember to the outer conductor of the cable means d lid bi mounted i hi hcylind i l b comprising a resilient split sleeve coaxial with the boremeans within the bore providing radially inwardly extendand disposedbetween the ledge M8118 and an inner end ing circumferential ledgemeans, the means for securing Wan P P i the f- Said 8 the body member tothe outer conductor of the cable and said end f being P'P with fgcomprising a resilient split sleeve coaxial with the boremeansml'nplessflon 0f the Sleeve and disposed heme", the ledge means andan inner end response to relative axial movement of the ferrule and wallprovided on the ferrule member, said ledge means ledge means towardeachother, said receptacle being and said inner end n being providgd withcamming provided with engag ng means for detachably engaging means tocause radial compression of the sleeve in f sald '"f p having bearing""F response to relative axial movement of the ferrule and Peanng 3 5'and 'f the membe' f l ledge means toward each other, said rmptade beingagainst the split sleeve, the insulating means supporting provided withengaging means for detachably engaging the socket compnses a centrallyapertured bead extendthe body member said receptacle having bearingmeans ing across the bore, and the socket having a portion for bearingagainst and moving the ferrule member axially thereof q s through theaperture! bead the against the split sleeve, a socket member supportedin the a eftendmg 'f' the aFfemfred bead and with radially extending proecting means respectively receptacle and provided with an opening whichis substantially conical and divergent toward one end of said socket.

abutting opposed surfaces of the bead for captivating the socket againstaxial movement.

4. The structure as recited in claim I, wherein one end of saidreceptacle is provided with means for detachably connecting thereceptacle to a housing for a circuit board.

3. A coaxial line tenninal adapter element for detachable connection ofa receptacle, comprising:

a hollow conductor body member having a cylindrical bore therethrough,means in said bore for conductively secur-

1. A coaxial line terminal adapter element for detachable connection of a receptacle, comprising: a hollow conductor body member having a cylindrical bore therethrough, means in said bore for conductively securing the body member to the end portion of an outer conductor of a coaxial line, insulating means mounted within the bore, a collet having an unobstructed opening therethrough for receiving the inner conductor of the line supported by said insulating means centrally of the bore, the collet being longitudinally slotted to provide a socket having a plurality of fingers between which the central conductor of the coaxial line slidably extends when the outer conductor of the coaxial line is disposed in the body member, a ferrule member supporting the insulating means and slidably mounted within the cylindrical bore, means within the bore providing radially inwardly extending circumferential ledge means, the means for securing the body member to the outer conductor of the cable comprising a resilient split sleeve coaxial with the bore and disposed between the ledge means and an inner end wall provided on the ferrule member, said ledge means and said inner end wall being provided with camming means to cause radial compression of the sleeve in response to relative axial movement of the ferrule and ledge means toward each other, said receptacle being provided with engaging means for detachably engaging the body member, said receptacle having bearing means for bearing against and moving the ferrule member axially against the split sleeve, said receptacle provided with a bore therethrough, and insulating means provided within the receptacle bore for supporting a conductive socket member concentrically therewithin, said socket member including an opening to receive the spring fingers therein.
 2. A coaxial line terminal adapter element for detachable connection of a receptacle, comprising: a hollow conductor body member having a cylindrical bore therethrough, means in said bore for conductively securing the body member to the end portion of an outer conductor of a coaxial line, insulating means mounted within the bore, a collet having an unobstructed opening therethrough for receiving the inner conductor of the line supported by said insulating means centrally of the bore, the collet being longitudinally slotted to provide a socket having a plurality of fingers between which the central conductor of the coaxial line slidably extends when the outer conductor of the coaxial line is disposed in the body member, a ferrule member supporting the insulating means and slidably mounted within the cylindrical bore, means within the bore providing radially inwardly extending circumferential ledge means, the means for securing the body member to the outer conductor of the cable comprising a resilient split sleeve coaxial with the bore and disposed between the ledge means and an inner end wall provided on the ferrule member, said ledge means and said inner end wall being provided with camming means to cause radial compression of the sleeve in response to relative axial movement of the ferrule and ledge means toward each other, said receptacle being provided with engaging means for detachably engaging the body member, said receptacle having bearing Means for bearing against and moving the ferrule member axially against the split sleeve, a socket member supported in the receptacle and provided with an opening which is substantially conical and divergent toward one end of said socket.
 3. A coaxial line terminal adapter element for detachable connection of a receptacle, comprising: a hollow conductor body member having a cylindrical bore therethrough, means in said bore for conductively securing the body member to the end portion of an outer conductor of a coaxial line, insulating means mounted within the bore, a collet having an unobstructed opening therethrough for receiving the inner conductor of the line supported by said insulating means centrally of the bore, the collet being longitudinally slotted to provide a socket having a plurality of fingers between which the central conductor of the coaxial line slidably extends when the outer conductor of the coaxial line is disposed in the body member, a ferrule member supporting the insulating means and slidably mounted within the cylindrical bore, means within the bore providing radially inwardly extending circumferential ledge means, the means for securing the body member to the outer conductor of the cable comprising a resilient split sleeve coaxial with the bore and disposed between the ledge means and an inner end wall provided on the ferrule member, said ledge means and said inner end wall being provided with camming means to cause radial compression of the sleeve in response to relative axial movement of the ferrule and ledge means toward each other, said receptacle being provided with engaging means for detachably engaging the body member, said receptacle having bearing means for bearing against and moving the ferrule member axially against the split sleeve, the insulating means supporting the socket comprises a centrally apertured bead extending across the bore, and the socket having a portion thereof extending through the apertured bead with the socket extending from the apertured bead and provided with radially extending projecting means respectively abutting opposed surfaces of the bead for captivating the socket against axial movement.
 4. The structure as recited in claim 1, wherein one end of said receptacle is provided with means for detachably connecting the receptacle to a housing for a circuit board. 